1. Field of the Invention
The present invention relates to an X-ray imaging apparatus and, more particularly to an X-ray imaging apparatus in which an X-ray imaging unit having X-ray imaging means is rotatably supported by a rotatably supporting pedestal.
2. Description of the Related Art
A conventional X-ray imaging apparatus 10 having an arrangement as mentioned above is schematically shown in FIG. 1. In FIG. 1, reference numeral 12 denotes a rotatably supporting pedestal installed, for example, on the floor of a building of a hospital, and numeral 14 denotes an X-ray imaging unit having X-ray imaging means 16a and 16b and rotatably supported on the rotatably supporting pedestal 12.
The X-ray imaging unit 14 has a vertically telescopically supporting post 18 rotatably supported on the rotatably supporting pedestal 12. A rotary drive source, not shown, having a rotatably driving shaft 20 protruding horizontally is stored in the vertically supporting post 18, and a coupling piece 22a protruding laterally from a partially circular-shaped arm guide 22 is attached to the rotatably driving shaft 20.
The arm guide 22 circumferentially movably supports a C-shaped supporting arm 24. The X-ray imaging means 16a and 16b are supported at both ends of the supporting arm 24.
One X-ray imaging means 16a is an X-ray emitting unit having an X-ray source, and the other X-ray imaging means 16b is an X-ray film cassette, a television camera, a movie camera, etc. the both two cameras being used together with an image intensifier. The television camera, the movie camera, and the X-ray film cassette are selectively used in response to its utility.
A bed 28 on which a patient 26 is laid is disposed near the conventional X-ray imaging apparatus 10 constructed as mentioned above. The bed 28 has a lower structure installed on the above-described floor and an upper structure mounted on the lower structure so as to be movable in its longitudinal direction with respect to the lower structure, on the upper structure the patient 26 being laid.
FIG. 1 shows the vertically imaging state of the X-ray imaging apparatus 10. In the bed 28, the upper structure on which the patient 26 is laid is so moved in its longitudinal direction relative to the lower structure that the end of the upper structure is disposed between the X-ray imaging means 16a and 16b at both ends of the supporting arm 24 on the arm guide 22 disposed at a vertical position.
In the X-ray imaging apparatus 10, when the supporting arm 24 is moved in the circumferential direction of the arm guide 22 as shown by bi-directional arrows A, the angle of the X-ray to be emitted to the patient 26 to cross the patient 26 between a pair of the X-ray imaging means 16a and 16b varies in the longitudinal direction of the bed 28 (i.e., in the longitudinal direction of the patient 26).
In the X-ray imaging apparatus 10, when the rotatably driving shaft 20 is rotated in both the directions shown by bi-directional arrows B by a rotary drive source, not shown, in the vertically supporting post 18, the angle of the X-ray to be emitted to the patient 26 between a pair of the X-ray imaging means 16a and 16b to cross the patient 26 varies in the lateral direction of the bed 28 (i.e., in the lateral direction of the patient 26).
In the X-ray imaging apparatus 10, the vertically supporting post 18 is vertically telescopically extended or contracted to contact or separate one X-ray imaging means 16a as an X-ray emitting unit with or from the patient 26.
When the X-ray imaging is not executed by the X-ray imaging apparatus 10, the vertically supporting post 18 is rotated from the position shown in FIG. 1 in either one of both directions shown by bi-directional arrows C around the rotational center line R of itself to move the arm guide 22 and the supporting arm 24 and hence a pair of the X-ray imaging means 16a and 16b to an X-ray imaging rest position, not shown, in which they are separated sidewisely from the bed 28 (i.e., sidewisely from the patient 26).
Markers 30a and 30b indicating that a pair of the X-ray imaging means 16a and 16b are disposed at the X-ray imaging position opposed to the patient 26 on the bed 28 as shown in FIG. 1 are provided on the lower end of the vertically supporting post 18 and the rotatably supporting pedestal 12.
An electromagnetic brake, not shown, is disposed between the lower end of the vertically supporting post 18 and the rotatably supporting pedestal 12, and the electromagnetic brake is used to hold the vertically supporting post 18 to the X-ray imaging position shown in FIG. 1. The rotation of the vertically supporting post 18 between the above-mentioned X-ray imaging rest position and the X-ray imaging position is conducted by man-power.
A work for disposing the X-ray imaging unit 14 at the X-ray imaging position in the conventional X-ray imaging apparatus requires a relatively long time, because the inertial moment of the X-ray imaging unit 14 is large so that it is difficult to so operate the X-ray imaging unit 14 by man-power as to bring a pair of markers 30a and 30b into coincidence. It is difficult to accurately stop the X-ray imaging unit 14, having a large inertial moment and once started moving, at the X-ray imaging position where the pair of markers 30a and 30b are coincident, and it is necessary to repeat the position correcting work.
If a relatively large force is applied to either one of the pair of X-ray imaging means 16a and 16b radially separated from the rotational center line R of the vertically supporting post 18 after the X-ray imaging unit 14 is disposed at the X-ray imaging position, the braking force of the electromagnetic clutch, not shown, might not oppose the rotary moment generated at the X-ray imaging unit 14 by the above relatively large force.